Air pumps have long been employed to inflate various articles, such as pneumatic tires, air mattresses, footballs and basketballs, inflatable toys, and the like. By their very nature, many of these articles need to be inflated in field environments, far from service stations or other facilities having installed air compressors. Consequently, a great many types of portable air pumps have been used or proposed, with varying degrees of success.
Perhaps the best known example of a portable air pump is the hand-operated reciprocating type, which is frequently carried clipped to the frame tubes of a bicycle. These pumps typically have a single-acting piston and cylinder, the piston being operated by means of a long rod to which a handle is attached. The cylinder and handle are gripped in opposite hands and reciprocated back and forth to drive air out of the cylinder and into the article to be inflated. While these prior art hand-operated reciprocating air pumps have the advantage of simplicity, they also exhibit a number of shortcomings. Firstly, they are fairly slow to operate, the speed of the reciprocating action being limited to that with which the operator can move his hands back and forth relative to one another. This disadvantage becomes quite burdensome when inflating relatively large articles which require significant volumes of air. Furthermore, inasmuch as the handle directly operates the piston rod, these pumps provide no mechanical advantage to assist the operator; consequently, it can be very difficult to attain high air pressures (as required by many modern bicycle tires) using such pumps. Moreover, since such pumps typically employ pistons and cylinders having small diameters and very long strokes, they are ordinarily quite long and thus difficult to stow. The long cylinders and piston rods are also typically made of metal, rendering it difficult to make such pumps as light as may be desired.
The need for portable air pumps that are compact, light, and fast acting has become more pronounced in recent years, particularly with the advent of very lightweight racing and touring bicycles. For example, speed of operation and minimum weight can be crucial factors in various competitive events, such as triathlons, which involve the use of bicycles.
A number of attempts have been made to employ the drive system or motion of the bicycle itself to operate an air pump. For the most part, these pumps have been mounted to turn with the wheel of the vehicle so as to inflate the tire while the vehicle is in motion. For example, U.S. Pat. No. 1,169,705 to Wilkes (1916) shows a pumping apparatus having a pump cylinder, with a piston being positioned in the cylinder and driven by a piston rod. This assembly is mounted to the hub of the wheel of a motorcycle and rotates therewith. There is a linkage having a roller that extends out through the spokes of the wheel so as to be activated by a track, which is fixed to the frame of the vehicle, causing the piston rod and piston to reciprocate so as to pump air through a flexible hose into the tire on the wheel.
A variety of other air pumps have been proposed, which, like that of Wilkes, are mounted to the hub of a wheel so as to rotate therewith and pump air to a tire on the wheel. For example, U.S. Pat. No. 797,447 to Merry (1905) shows a rotating, hub-mounted piston assembly that engages a slanted disc on the frame of the bicycle so as to impart a reciprocating motion to the piston. U.S. Pat. No. 744,483 to Carlberg (1903) shows a pump assembly that rotates with the wheel and which has a lever that extends from the wheel and cooperates with a fixed cam plate on the bicycle frame so as to reciprocate the cylinder along a wire guide, which is fixed to the wheel rim. U.S. Pat. No. 652,997 to Crandall (1900) shows a pump assembly that rotates with the wheel of a bicycle and has a protruding cam follower, which engages an eccentric cam mounted to the bicycle frame so as to impart a reciprocating motion to a piston in the pump cylinder. U.S. Pat. No. 624,417 to Wickersham et at. (1899 ), U.S. Pat. No. 596,223 to Wickersham et al. (1897), and U.S. Pat. No. 559,418 to Spencer (1896) show other air pump arrangements having pinion gears that protrude from the rotating pump assemblies and engage larger stationary gears, which are mounted to the vehicle frames; rotation of the pinion gears operates crank arms, which in turn reciprocate pistons of the pumps.
A variety of other devices have been proposed which are driven by the chain and sprocket drive of a bicycle, or which otherwise utilize the rotational motion of bicycle components. For example, U.S. Pat. No. 681,565 to McCune (1901) shows a fan which is mourned adjacent to the handlebars of a bicycle, the blades of which are rotated by means of a belt drive from the crank assembly of the bicycle. U.S. Pat. No. 868,658 to Hamacher (1907) discloses a bicycle in which movement of the rider's feet apparently reciprocates pump cylinders to generate compressed air that acts against vanes of a drum to cause rotation of a shaft, which is presumably attached to a drive for the back wheel. U.S. Pat. No. 3,283,997 to Bambenek et al. discloses a portable ventilator in which a stationary bicycle has a chain and sprocket drive, which rotates a large pulley, which in turn drives a belt that provides power to the ventilating apparatus. U.S. Pat. No. 4,677,328 to Kumakura discloses a bicycle generator having a stator which is fixed to the bicycle frame land a rotor, which rotates with the flange of the wheel.
It will be appreciated that each of the above-described bicycle-driven devices adds undesirable weight to the bicycle to which it is mounted. Furthermore, notably with respect to the air pumps, many of these devices are characterized by complicated, heavy, and inefficient mechanical linkages. The rotating pump assemblies would also have a deleterious effect on the balance of the wheels to which they are affixed. Furthermore, inasmuch as these devices operate while the vehicle is in motion, they would appear to be able to inflate only that tire which rotates on the wheel together with the pump; these devices are thus unsuitable for inflating the other tire of the bicycle, or for inflating articles which are separate from the bicycle, such as air mattresses, footballs, or the like.
A number of air pumps are known apart from those which are bicycle driven. Amongst these is that shown in U.S. Pat. No. 2,472,647 to Coyins (1949), which discloses a double-acting reciprocating pump in which there are two pistons having an interconnecting element. The interconnecting element has a slot which extends at right angles to the direction of reciprocation of the pistons, and which is also at right angles to the axis of a crank. An end portion of the crank arm is received in the slot and as the crank arm rotates, the interconnected pistons are moved back and forth for the pumping action. There are inlet and outlet valves for each cylinder, the outlet valves being able to be connected to a common output line so as to obtain a more or less constant flow of air from the pump. Similar piston-cylinder arrangements are shown in U.S. Pat. No. 3,517,652 to Albertson (1970), which discloses a two-stroke engine, and U.S. Pat. No. 3,451,276 to Wadlow et al. (1969), which discloses an actuator mechanism. None of the devices described in this paragraph is adapted for use with a bicycle-drive mechanism.
U.K. Patent No. 724,960 to Mehta (1955) does disclose a single-piston reciprocating air pump adapted for use with a bicycle drive mechanism. The air pump is attached to the frame of the bicycle, at a location above the drive chain. A pivotable mechanical linkage extends downwardly from the air pump towards the drive chain of the bicycle, and a sprocket disposed on the distal end of the mechanical linkage engages the drive chain. Engagement of the sprocket with the drive chain is maintained by a clamp attached to the sprocket and to the frame of the bicycle at a location below the upper run of the bicycle chain. Wing nuts permit the clamp to be loosened, and reclamped to the frame of the bicycle at a location that disengages the sprocket from the drive chain when it is not desired to operate the air pump.
However, the air pump disclosed by Mehta has numerous problems because it is so complicated and inefficient that it likely will not work reasonably well for its intended purpose. First, the mechanical linkage is of substantial length having two pivot points. The substantial length of the linkage results in a large lever arm that causes relatively large forces and torques to be applied to the air pump. Thus, the only material of which the air pump can be made that can structurally withstand the relatively large forces and torques is metal, which undesirably adds significant weight to the bicycle.
Second, the substantial length of the mechanical linkage requires precise longitudinal alignment of the air pump on the bicycle frame, which is difficult to achieve with a device clamped to the frame of a bicycle. Moreover, any shocks applied to the bicycle, which are common, will require precisely re-aligning the device of Mehta on the bicycle.
Third, the mechanical linkage is exposed to the environment, which probably will result in corrosion of the metal linkage, buildup of contaminants on the pivot points of the linkage, and introduction of contaminants into the pumping assembly.
Fourth, the air pump includes a single reciprocating piston, which is inefficient compared to a doubly-opposed piston arrangement. Unfortunately, with the arrangement disclosed by Mehta, there is no reasonable way that a doubly-opposed piston arrangement could be used.
Finally, the sprocket is designed to be disengaged from the drive chain by loosening wing-nuts that tighten the clamp mounted to the bicycle frame. The problem here, however, is that is very difficult to re-engage the sprocket with the drive chain when desired because the sprocket must be tightly held against the drive chain while tightening the wing-nuts.
Accordingly, there is a need for a portable air pump for inflating bicycle tires and other articles, which is light in weight, efficient and fast in operation, and usable on bicycles having chain tensioning derailleurs. Furthermore, there is a need for such a device which provides a mechanical advantage so as to permit an operator to inflate articles to high pressures, as well as for such a device which is compact and readily stowable.